The invention relates to a method for concentrating solutions containing macromolecules, more particularly solutions of protein molecules, to a defined end volume and a filter for carrying out this method.
In the publication No. 1/130 F of AMICON Division, W.R. Grace & Co - AMICON GMBH Witten, a commercially available disposable ultrafilter is described for the static concentration of small amounts of macromolecular solutions. This ultrafilter has eight separated upright chambers which can be used at different times for different solutions. The chambers are bound by upright membranes with selective permeability. An absorbing material is placed on the back of these membranes. This absorbing material, through capillary action, sucks the liquid phase from the solutions in the chambers and into the absorbing material. The macromolecular constituents are thereby concentrated in the solutions remaining in the chambers. The level of the solutions in the chambers drops. The chambers are provided with marks which indicate the degree of concentration. As soon as the desired mark is reached in a chamber during the concentration, the solution still present with the macromolecules is removed from the chamber. A lower section of the membrane is made impermeable in order to hinder further concentration. In the known concentration method a batch process is worked. This results in a local thickening of a stationary solution by removal of the liquid phase. The process of concentration is restricted by the capacity of the absorbing material. If larger quantities of solution are to be concentrated, the known device leads to an exceptionally complicated method of operation. A degree of concentration of any level cannot be reached. With this method a part of the macromolecules is deposited on the membrane as the liquid phase is sucked through same. These macro molecules remain sticking to the membrane and do not pass into the concentrate as the solution sinks further down. This loss of substance causes the effectiveness of the concentration method to be irreversibly reduced.
U.S. Pat. No. 4,632,761, column 1, lines 37 to 41, it is expressly stated that with the ultrafilter previously described, a complete drying of the filtered constituents is produced by surface tensions which act on the concentrate in the area of the filter section which has been rendered impermeable together with capillary suction forces. The preparation is thereby unusable. This danger of drying out is pointed out by the manufacturer through a warning packed with the ultrafilters.
From U.S. Pat. No. A 4,123,224 a method and device are known for concentrating solutions containing macromolecules. The solution is introduced into a concentration chamber defined by a filter. An absorbent material is placed on the filtrate side of the filter. The concentrate is collected in a concentrate chamber adjoining the concentration chamber and the filter surface becomes smaller towards the concentrate chamber. The concentrate is collected in the concentrate chamber with defined end volume lying screened from the filter leaf.